The present invention relates to a stator for synchronous motors having more than two poles.
It is known that single-phase permanent-magnet synchronous motors are currently provided by means of a stator configuration S which is shaped like a tuning fork (see FIG. 1 of the accompanying drawings), which has been very successful thanks to its low cost arising from its extreme constructive simplicity.
The windings, not shown in FIG. 1, are formed on spools with winding machines which have a high production rate, can be easily automated and therefore have an unbeatable investment/productivity ratio.
The coils are then very easily fitted on the respective pole shoes of the stator.
Moreover, FIG. 1 clearly shows that the process for blanking the metal laminations that compose the stator pack minimizes waste, thanks to the tuning-fork geometry, which allows two contours to interpenetrate.
In synchronous motors having a stator with more than two poles, the structure is necessarily more complicated.
FIG. 2, for example, illustrates the diagram of a four-pole stator in which there is a ring A on the inside whereof there are four dovetail slots B for the interlocking insertion of complementarily shaped ends C of pole shoes D.
In this case also, the windings, not shown, are produced on spools by means of winding machines and the coils are fitted on the pole shoes D.
Finally, the pole shoes D are inserted in the ring A with an interlocking coupling.
In this case, construction of the stator is complicated, because the ring A becomes very expensive as it entails a large amount of waste in the blanking process, while the interlocking coupling of the pole shoes D with the ring A causes problems related both to coupling tolerances (if they are too small, assembly is particularly difficult, whereas if they are too large, one introduces a loss in the magnetic circuit and an insufficient structural solidity of the stator, with the risk of introducing unwanted vibrations) and to assembly, which must occur at right angles to the plane of the stator, with consequent complications in the assembly process.
In order to solve these problems, motors have been devised in which the stator (see FIG. 3) is constituted by a plurality of sectors E which are joined at their ends, forming as a whole a closed annular structure.
A pole shoe F protrudes from each sector E and is monolithic therewith.
The ends G are complementarily shaped, forming male-female interlocking couplings H, and constitute, as a whole, seats I for mutual fixing screws, not shown.
In this case, the monolithic annular element is eliminated, but there is still the need to interlock the last sector E by acting on a plane which is perpendicular to the stator plane, with the consequent coupling problems, although greater structural solidity is achieved by means of the screws.
The interlocking couplings H moreover introduce asymmetry problems which make it necessary to orientate the pack during assembly.
The amount of waste is reduced with respect to the preceding case.
The aim of the present invention is to provide a stator for synchronous motors having more than two poles which allows to fit coils wound beforehand on spools by means of winding machines in a simple manner on each one of the poles before assembly.
Within the scope of this aim, a consequent primary object is to provide a stator which avoids the need to orientate the components during mutual assembly.
Another object is to eliminate any kind of interlocking between the parts, so as to eliminate the problems related to the mechanical coupling tolerance in order to facilitate assembly.
Another important object is to minimize the amount of waste during the blanking process.
These and other objects which will become better apparent hereinafter are achieved by a stator for synchronous motors with more than two poles, comprising a plurality of sectors formed by lamination packs which are joined at their ends, forming as a whole a closed annular structure, at least one pole shoe protruding from each one of said sectors, characterized in that said ends define, at each connecting region, by respective facing shaped portions, at least one tab with opposite undercuts, one for each end, said tabs accommodating corresponding portions of an elastic connecting element which surrounds said tab and rigidly couples the sectors.